This invention relates to a display system. In a situation such as in an aircraft, where space is limited, there is a restriction on the number of instruments and displays that will fit in a given amount of panel space. For example, it would be desirable to locate an artificial horizon display near other navigational and control displays in fighter aircraft at the top of the instrument panel. However, in most modern fighters, the artificial horizon is placed near the bottom of the instrument panel, and the pilot, with his oxygen mask on, must alter his direction of gaze by more than 30.degree. to check the instrument. Problems of size and space restrictions for instruments are heightened by the need for redundancy of critical instruments. Due to the tight space restrictions, the panel layouts are not easily modified when an aircraft is reconfigured.
Conventional cockpit displays are typically of two types--electro-mechanical and cathode ray tube (CRT)--although liquid crystal displays, light emitting diode displays, and electroluminescent displays are also used. Beyond the space restrictions, other problems of conventional instrument displays include the production of canopy glare from instrument lighting which is distracting to the pilot. Conventional electro-mechanical multi-instrument panels are complex and the servicing of such panels is time-consuming and expensive. Electro-mechanical instruments provide a limited symbology, i.e. they are limited to alphanumeric characters or mechanical analog dials and read-outs.
To increase the amount of information displayed on the instrument panel without increasing the space requirements of the instruments, it may be desirable to selectively project an image, such as an image of an artificial horizon, onto a portion of the instrument panel which is occupied by existing switches, key pads, controls, and other non-display components. However, such light projection can be impractical because of the power required to compete with direct sunlight, and since normal reflection would introduce light into the cockpit area as unwanted reflections and glare, including reflections off of the cockpit canopy, a particularly significant problem during night-time flying.